For powering up an IC, conventionally such powering up is performed incrementally to avoid overstressing transistors. This incremental powering up may be performed by sequential voltage regulators; however, this adds cost.
Conventionally, powering down a device has not been incrementally controlled. Generally when a power supply is shut off, it does not instantaneously go down to zero volts. Rather, it gradually decreases to zero volts, and so conventionally powering down a device has not been incrementally controlled.
However, external and coupled to an output driver of an IC may be a capacitive load, such as may be provided by an external decoupling capacitor, a printed circuit board capacitance, and/or another external capacitance. Thus, depending on capacitive load, one device with a high capacitive load may discharge more slowly than another, even identical, device with a low capacitive load. Furthermore, a device with a large circuit load may drain or discharge more rapidly than a device with a small circuit load. Accordingly, depending on differences in capacitive load and/or circuit load among devices, such devices may discharge or charge at different rates. These differences may lead to one or more overstress conditions of on one or more transistors.
Accordingly, it would be desirable and useful to avoid an overstress condition of a transistor without having to use costly incremental voltage regulators.